Diet, food, and nutritional exposures and inflammatory bowel disease or progression of disease: an umbrella review

Inflammatory bowel disease (IBD), including Crohn's disease (CD) and ulcerative colitis (UC), are all contributing to substantial morbidity. Understanding the intricate interplay between dietary factors and the incidence and progression of IBD is essential for developing effective preventative and therapeutic strategies. This umbrella review comprehensively synthesizes evidence from systematic reviews and meta-analyses to evaluate these complex associations. Dietary factors associated with an increased incidence and/or progression of IBD include a high intake of red and processed meat, other processed foods, and refined sugars, together with a low intake of vegetables, fruits, and fiber. For most other food groups, results are mixed or indicate no clear associations to IBD, CD and UC. There seems to be some differences between UC and CD and their risk factors, with increased intake of dietary fiber being inversely associated with CD incidence but not clearly associated with UC. Dietary fiber may contribute to maintaining the gut epithelial barrier and reduce inflammation, often through interactions with the gut microbiota. This seems to play an important role in inflammatory mechanisms in the gut and IBD incidence and progression. Diets low in fermentable saccharides and polyols can alleviate symptom burden, but there are concerns regarding its impact on the gut microbiota and its nutritional adequacy. Mediterranean diets, vegetarian diets, and a diet low in grains, sugars, and lactose (specific carbohydrate diet) are also associated with lower incidence and/or progression of IBD. The associations for dietary patterns are mirrored by inflammatory biomarkers. IBD is typically treated pharmaceutically, however, many have suboptimal response to medical treatments. The findings from this umbrella review could provide evidence for nutritional counselling and be a valuable addition to traditional treatment plans of IBD. This systematic review has been registered with PROSPERO (CRD440252).